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6 Path Categories
 6.1 Operations
 6.2 GAP categories
 6.3 Constructors
 6.4 Attributes

6 Path Categories

6.1 Operations

6.1-1 GroebnerBasis
‣ GroebnerBasis( C, rels )( operation )

Returns: a dense list

The input is a path category C and a list rels consisting of pairs of parallel morphisms in C. The output is the Groebner basis of rels.

6.1-2 ReducedGroebnerBasisWithGivenGroebnerBasis
‣ ReducedGroebnerBasisWithGivenGroebnerBasis( C, groebner_basis )( operation )

Returns: a dense list

The input is a path category C and a Groebner basis groebner_basis consisting of pairs of parallel morphisms in C. The output is the reduced Groebner basis of groebner_basis.

6.1-3 ReducedGroebnerBasis
‣ ReducedGroebnerBasis( C, rels )( operation )

Returns: a dense list

The input is a path category C and a list rels consisting of pairs of parallel morphisms in C. The output is the reduced Groebner basis of rels.

6.1-4 IsDescendingForMorphisms
‣ IsDescendingForMorphisms( C, f, g, admissible_order )( operation )

Returns: a boolean

The input is a path category C, two parallel morphisms f, g and a string admissible_order which takes one of the following two values "Dp" or "dp". The output is whether f \succ g with respect to the specified admissible order. "Dp" stands for the left-length-lexicographic order under which f \succ_{\mathtt{Dp}} g if MorphismLength(f) \succ MorphismLength(g); or MorphismLength(f)=MorphismLength(g) and the first nonzero entry in MorphismIndices(f)-MorphismIndices(g) is negative. "dp" stands for the right-length-lexicographic order under which f \succ_{\mathtt{dp}} g if MorphismLength(f) \succ MorphismLength(g); or MorphismLength(f)=MorphismLength(g) and the last nonzero entry in MorphismIndices(f)-MorphismIndices(g) is negative. For example, if the quiver of C is defined by the string "(*)[x:*->*,y:*->*]", then

6.1-5 IsAscendingForMorphisms
‣ IsAscendingForMorphisms( C, f, g, admissible_order )( operation )

Returns: a boolean

The input is a path category C, two parallel morphisms f, g and a string admissible_order which takes one of the following two values "Dp" or "dp". The output is whether f \prec g with respect to the specified admissible order.

6.2 GAP categories

6.2-1 IsPathCategory
‣ IsPathCategory( arg )( filter )

Returns: true or false

The GAP category of path categories.

6.2-2 IsPathCategoryObject
‣ IsPathCategoryObject( arg )( filter )

Returns: true or false

The GAP category of objects in path categories.

6.2-3 IsPathCategoryMorphism
‣ IsPathCategoryMorphism( arg )( filter )

Returns: true or false

The GAP category of morphisms in path categories.

6.3 Constructors

6.3-1 PathCategory
‣ PathCategory( q )( operation )

Returns: a CAP category

The input is a CAP quiver q. The output is the path category of q, i.e., the category whose objects are the objects of q and whose morphisms are lists of morphisms in q, in which the target of any morphism is equal to the source of the next morphism.

6.3-2 ObjectConstructor
‣ ObjectConstructor( C, i )( operation )

Returns: a CAP category object

The input is a path category C of CAP quiver q and a positive integer i. The output is the i'th object in C.

6.3-3 MorphismConstructor
‣ MorphismConstructor( C, s, l, support, t )( operation )

Returns: a CAP category object

The input is a path category C of CAP quiver q, two objects s, t a nonnegative integer length and a list support of length l consisting of morphisms in q where the target of each morphism is equal to the source of the next morphism. The output is the morphism in C whose length is l and whose support is support.

6.3-4 AssignSetOfObjects
‣ AssignSetOfObjects( C[, str] )( operation )

Returns: nothing

Assigns the objects of C to global variables. Names of the variables are the concatenation of str with the labels of the objects. The default value of str is the empty string.

6.3-5 AssignSetOfGeneratingMorphisms
‣ AssignSetOfGeneratingMorphisms( C[, str] )( operation )

Returns: nothing

Assigns the generating morphisms of C to global variables. Names of the variables are the concatenation of str with the labels of the generating morphisms. The default value of str is the empty string.

6.4 Attributes

6.4-1 OppositePathCategory
‣ OppositePathCategory( C )( attribute )

Returns: a path category

Returns the opposite category of the path category C.

6.4-2 CategoryFromNerveData
‣ CategoryFromNerveData( C )( attribute )

6.4-3 UnderlyingQuiver
‣ UnderlyingQuiver( C )( attribute )

Returns: a list of CAP category objects

Returns the defining quiver of the path category C.

6.4-4 ObjectIndex
‣ ObjectIndex( v )( attribute )

Returns: a positive integer

Returns the index of the object v.

6.4-5 ObjectLabel
‣ ObjectLabel( v )( attribute )

Returns: a string

Returns the label of the object v.

6.4-6 MorphismLength
‣ MorphismLength( alpha )( attribute )

Returns: a positive integer

Returns the length of alpha.

6.4-7 MorphismSupport
‣ MorphismSupport( alpha )( attribute )

Returns: a dense-list of CAP quiver morphisms

Returns the list of morphisms in the underlying quiver which defines alpha.

6.4-8 MorphismIndices
‣ MorphismIndices( alpha )( attribute )

Returns: a dense-list of positive integers

Returns the indices of the morphisms in MorphismSupport(alpha).

6.4-9 MorphismLabel
‣ MorphismLabel( alpha )( attribute )

Returns: a positive integer

Returns the label of the morphism alpha.

6.4-10 IsFinitePathCategory
‣ IsFinitePathCategory( C )( property )

Returns: a boolean

Returns whether C can be enriched over the category of finite sets.

6.4-11 HasFiniteNumberOfMacaulayMorphisms
‣ HasFiniteNumberOfMacaulayMorphisms( C, mors )( operation )

Returns: a boolean

The input is a path category C and a list of morphisms mors in C (mors is usually the leading terms of a Groebner basis). The output is whether almost all morphisms of C are multiples of elements in mors. In other words, whether the number of morphisms that are not multiples of elements in mors (i.e., Macaulay monomials) is finite.

6.4-12 MacaulayMorphisms
‣ MacaulayMorphisms( C, mors )( operation )

Returns: a boolean

The input is a path category C and a list of morphisms mors in C (mors is usually the leading terms of a Groebner basis). The output is the Macaulay monomials with respect to mors.

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